In practice, it is known that, for example in the production of sausage-shaped products, like sausages, filling material is fed by a filling machine through a filling tube of a clipping machine into a tubular or bag-shaped packaging casing which is temporarily stored on the filling tube and which is closed at its front end, i.e. the end pointing in the feeding direction of the filling material, by, for example, a closure means, like a closure clip, or by a fusing line at this end, respectively. The tubular packaging casing is pulled-off from the filling tube while being filled filling material fed into the casing by the feeding pressure. At least during the filling process, a casing brake applies a frictional force to the tubular packaging casing while being pulled-off from the filling tube, in order to control the pull-off speed and to ensure an at least approximately constant filling degree.
After a predetermined volume of filling material has been filled into said tubular packaging casing, gathering means with a first and a second displacer unit which can each be formed by a pair of reversibly movable displacement elements, form a plait-like portion of the tubular packaging casing, which is at least substantially free of filling material. By moving the first and second displacer units relative to each other, the length of the plait-like portion may be varied. For example, products being completely filled with filling material, or tightly filled, are usually provided with a relatively short plait-like portion whereas products being only partly filled with filling material are provided with a relatively long plait-like portion to produce a slack filled sausage-shaped product. The clipping machine then places and closes at least one closure clip at the plait-like portion forming the rear end of the sausage or bag-shaped product, i.e. the end pointing opposite to the feeding direction by respective closing tools which are reversibly movable towards the plait-like portion.
From DE laid open document 196 44 074, a clipping machine is known, which comprises first and second closing tools as well as first and second displacer units each including a pair of displacer elements which are linearly movable between their opened and closed position for gathering a filled tubular casing. The closing tools are driven by respective piston/cylinder drives. The displacer elements of the displacer units are also linearly movable by a respective separate drive means. Additionally, the displacer units include an additional drive for linearly moving the displacer units relative to each other for forming the plait-like portion on which the closure means are to be placed by the closing tools.
DE laid open document 1 786 585 discloses a clipping machine which includes gathering means for gathering a filled packaging casing, and closing means for closing the filled packaging casing. The gathering means include a first and a second displacer unit each having a pair of displacer elements, wherein the second displacer unit is axially movable away from and towards to the first displacer unit, for forming a plait-like portion on which at least one closure clip may be placed for closing the filled packaging casing. The movement of the gathering means for gathering the filled packaging casing, the movement of the closing means for placing and closing the at least one closure clip, and the movement of the second displacer unit away from and towards to the first displacer unit, are derived from a common drive.
In the case that the movement of all moved major devices of a clipping machine, like the closing tools, the gathering means, particular the first and second displacer units, or the like, are driven by a common drive, and are coupled to each other in a fixed relationship, e.g. via mechanical coupling means, like gear transmissions, a minimum of control amount is necessary for controlling the clipping machine. On the other hand, such a machine provides only a minimum flexibility in changing the production process. In case that each movable major devices of a clipping machine has its own drive, a huge construction and control amount is necessary for controlling such a clipping machine which provides a maximum flexibility in adapting the production process, e.g. to different products to be produced.